Subject in Typescript

Subject.ts

class Subject implements Observable {
    private observers: Observer[] = [];
    subscribe(observer: Observer) {
        this.observers.push(observer);
    }
    unsubscribe(observer: Observer) {
        this.observers = this.observers.filter((o) => {
            return o !== observer
        })
        console.log('observer detached...' + observer.constructor.name);
    }
    notify() {
        this.observers.forEach((o) => {
            o.update(this);
        })
    }

}